Why does Christianity have so many rules about sex?

It can feel like Christianity has an unusually long list of rules about sex, but the reasoning isn't arbitrary restriction—it's a particular view of what sex actually is and what it's for.

Scripture treats sex as meaningful and powerful, not casual or morally neutral, because it involves a whole person, body included: "the person who is sexually immoral sins against his own body," Paul writes, because "your body is a temple of the Holy Spirit" (1 Corinthians 6:18–19).

The Bible connects sex to the deepest kind of commitment between two people—described in Genesis as two people becoming "one flesh" (Genesis 2:24). Sex outside that kind of full commitment isn't treated as wrong because pleasure is bad, but because it detaches something designed for whole-life commitment from the commitment it's meant to go with.

None of this means Christianity treats sex as shameful. Song of Songs, an entire book of the Bible, is a joyful, unembarrassed celebration of romantic and physical love within marriage. The "rules" exist around something the Bible actually considers good.